Estimation of Shallow Shear Velocity Structure in a Site with Weak Interlayer Based on Microtremor Array
Giuseppe Marano
Round 1
Reviewer 1 Report
The present study discusses the adoption of the multichannel microtremor survey, a geophysical method to investigate seismic site conditions. Specifically, the authors focused on sites with weak interlayers, which local effects may represent a high potential risk, especially for urban areas. The authors have been interested to define the shear wave (S-wave) velocity structure that, according to the microtremor method, is able to provide also sediment thickness or bedrock depth. S-wave seismic inversion was performed on two typical stratigraphic structures in Wuhan, Hubei Province, China, demonstrating evidencing a weak interlayer stratum consistent with drilling data, and with a limited error with respect to direct in-situ borehole data testing. The present study is well-written and organized, the results sound interesting, and I recommend the work to be accepted for publication in your journal if and only if the authors introduce the following minor revisions and changes:
• The authors are invited to modify the title to be immediately clear on which velocity they are estimating in the current work (shear velocity), i.e. “Estimation of shallow shear velocity structure in site with weak interlayer based on microtremor array” .
• Pag 4 line 135, the authors state that “Rayleigh wave energy accounts for more than 70% of the total signal energy”, please provide a bibliographic reference to support this sentence.
• In order to improve and complete the state-of-art literature review, the authors are invited to comment on the following recent works within the introduction section:
â—‹ Lin, P., Zheng, W., Huang, B., & Zhang, H. (2015). Seismic fortification analysis of the Guoduo gravity dam in Tibet, China. Shock and Vibration, 2015.
â—‹ Vanzi, I., Marano, G.C., Monti, G., Nuti, C.; A synthetic formulation for the Italian seismic hazard and code implications for the seismic risk (2015) Soil Dynamics and Earthquake Engineering, 77, pp. 111-122. DOI: 10.1016/j.soildyn.2015.05.001
â—‹ Araya-Polo, M., Farris, S., Florez, M.: Deep learning-driven velocity model building workflow. The Leading Edge 38(11), 872–18729 (2019)
â—‹ Liu, H., Song, J., Li, S.: Seismic event identification based on a generative adversarial network and support vector machine. Frontiers in Earth Science 10 (2022)
• Why section 6. Discussion is placed after the conclusion section? Please place them before the conclusion and extend more the discussion section since it is too short.
• Do the author even consider possible future developments to work with seismic inversion imaging with innovative artificial intelligence and deep learning approaches? Please refer to the following studies and comment about the future perspective of integrating artificial intelligence into the current approach.
â—‹ Liu, H., Li, S., Song, J.: Discrimination between earthquake p waves and microtremors via a generative adversarial network. Bulletin of the Seismological Society of America 112(2), 669–679 (2022)
â—‹ Rosso, M. M., Marasco, G., Aiello, S., Aloisio, A., Chiaia, B., & Marano, G. C. (2023). Convolutional networks and transformers for intelligent road tunnel investigations. Computers & Structures, 275, 106918.
â—‹ Zhang, J., Sheng, G.: First arrival picking of microseismic signals based on nested u-net and wasserstein generative adversarial network. Journal of Petroleum Science and Engineering 195, 107527 (2020)
Author Response
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Author Response.pdf
Reviewer 2 Report
In this manuscript, microtremor linear array method is employed for ultimate identification of shallow velocity structure. The study focus is on two case studies. The manuscript is well written and communicates clearly. I recommend the manuscript for eventual publication following a revision based on below remarks:
1. Although GB 50011-2010 is addressed in the manuscript, the comparison with at least one international code is missing.
2. The discussions on the cost is weak. I would suggest removing all cost-related phrases from abstract, conclusions, etc. Or discuss with numbers for cost estimation.
3. Please make sure that figures 1 and 2(a) do not have copyright issues.
4. No paper is cited from the first author or corresponding author in the manuscript. please provide relevant previous studies by the authors.
5. Also, a considerable number of references are Chinese while the journal has international audience. please revise.
6. The conclusions suffer from lack of numeric outcomes. Please add the major numbers from the results of study.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Near-surface shear wave pofiles are important in earthquake engineering
applications.
This study is significant because it compares s a non-invasive method
(noise correlation) with an invasive in-situ method, showing good agreement.
A point that needs further explanation is the power(velocity-frequency)
plots in the figures and their relationship to the Aki's formula correllogram, as set out in the earler part of the figure. It looks to me like the false-color images are based on straight wavenumber-frequency array analysis (or rather velocity-frequency array analysis where velocity = frequency / wavenumber) and not on inversion of Aki's formula.
Are these images merely being used as "background" with the Aki's formula results the overlayed black like (which id my best guess of what they
represent)? Or something else?
If an inversion of the Aki formula correlogram is being performed, the authors need to show an observed correlogram (at least in the first figure), overlayed with the one predicted by the inversion. (By correlogram I mean the rho(omega) plot that looks like a bessel function).
This information is needed to ensure that the reader understands what's being portrayed in the figures.
Otherwise, the paper is fine and will be of interest in the earthquake engineering community.
Author Response
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